Photoelectric conversion device and manufacturing method of the same, and a semiconductor device

ABSTRACT

A photo-sensor having a structure which can suppress electrostatic discharge damage is provided. Conventionally, a transparent electrode has been formed over the entire surface of a light receiving region; however, in the present invention, the transparent electrode is not formed, and a p-type semiconductor layer and an n-type semiconductor layer of a photoelectric conversion layer are used as an electrode. Therefore, in the photo-sensor according to the present invention, resistance is increased an electrostatic discharge damage can be suppressed. In addition, positions of the p-type semiconductor layer and the n-type semiconductor layer, which serve as an electrode, are kept away; and thus, resistance is increased and withstand voltage can be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/276,036, filed Feb. 10, 2006, now pending, which claims the benefitof foreign priority applications filed in Japan as Serial No.2005-042926 on Feb. 18, 2005 and Serial No. 2005-121392 filed on Apr.19, 2005, all of which is incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric conversion device, moreparticularly, a photoelectric conversion device which is formed by usinga thin film semiconductor element and a method for manufacturing thephotoelectric conversion device. In addition, the present inventionrelates to an electronic device using a photoelectric conversion device.

2. Description of the Related Art

A number of photoelectric conversion devices generally used fordetecting an electromagnetic wave are known, and for example, aphotoelectric conversion device having sensitivity in ultra-violet raysto infrared rays are referred to as a photo-sensor in general. Aphoto-sensor having sensitivity in a visible radiation region with awave length of 400 nm to 700 nm is particularly referred to as aphoto-sensor for visible light, and a number of photo-sensors forvisible light are used for devices which need an illuminance adjustmentor on/off control depending on a human living environment.

In particular, in a display device, brightness in the periphery of thedisplay device is detected to adjust display luminance. It is becauseunnecessary electric-power can be reduced by detecting peripheralbrightness and obtaining appropriate display luminance. Specifically,such a photo-sensor for adjusting luminance is used for a cellular phoneor a personal computer (for example, refer to the Patent Document 1).

In addition, as well as peripheral brightness, luminance of back lightof a display device, particularly, a liquid crystal display device isalso detected by a photo-sensor to adjust luminance of a display screen(for example, refer to the Patent Documents 2 and 3).

Further, in a display device using a projector, the convergenceadjustment is conducted by using a photo-sensor. The convergenceadjustment is to adjust an image so that an image of each color of RGBdoes not generate discrepancy. By using a photo-sensor, a location of animage of each color is detected, and the image is arranged in the rightlocation (for example, refer to the Patent Document 4).

FIG. 6 shows a structure of a photo-sensor that has been usedconventionally. In FIG. 6, a first transparent electrode 1002 is formedover a substrate 1001, and a p-type semiconductor layer 1003, anintrinsic semiconductor layer 1004 and an n-type semiconductor layer1005, which serve as a photoelectric conversion layer, are formed overthe first transparent electrode 1002. Further, a second transparentelectrode 1006 is formed over the n-type semiconductor layer 1005. Then,a discrete insulating layer 1007 is formed to cover the transparentelectrodes 1002 and 1006, and contact holes are formed in the discreteinsulating layer 1007. Moreover, a first extraction electrode 1008connected to the first transparent electrode 1002 and a secondextraction electrode 1009 connected to the second transparent electrode1006 are formed.

In the photo-sensor shown in FIG. 6, since the transparent electrodes1002 and 1006 are formed, there is a problem that resistance is lowered,static electricity is discharged faster, and electrostatic dischargedamage is likely to be caused. In addition, an electric field isconcentrated on end portions of the p-type semiconductor layer 1003, theintrinsic semiconductor layer 1004 and the n-type semiconductor layer1005, which are the photoelectric conversion layer, so that there is aconcern that electrostatic discharge damage is more likely to be caused.

Further, since the transparent electrode 1006 is formed over the entiresurface of the n-type semiconductor layer 1005 which is an upper layerof the photoelectric conversion layer, and the transparent electrode1006 is formed over the entire surface of the p-type semiconductor layer1003 which is a lower layer of the photoelectric conversion layer,intensity of light that is incident to the photoelectric conversionlayer can be decreased.

-   [Patent Document 1] Japanese Patent Laid-Open No. 2003-60744-   [Patent Document 2] Japanese Patent No. 3171808-   [Patent Document 3] Japanese Patent No. 3193315-   [Patent Document 4] Japanese Patent Laid-Open No. 2003-47017

SUMMARY OF THE INVENTION

In view of the foregoing problems, it is an object of the presentinvention to provide a photo-sensor having a structure which cansuppress electrostatic discharge damage.

In the present invention, in order to solve the foregoing problems, onefeature of the invention is that a transparent electrode overlappingwith the entire surface of a light receiving region is not formed.Further, in the present invention, a p-type semiconductor layer of aphotoelectric conversion layer is used as one electrode, and an n-typesemiconductor layer is used as the other electrode. When the p-typesemiconductor layer and the n-type semiconductor layer are used as anelectrode, resistance is increased and electrostatic discharge damagecan be suppressed.

In addition, positions of the p-type semiconductor layer and the n-typesemiconductor layer, which serve as an electrode, are kept away; andthus, resistance is increased and the ability of the photo-sensor towithstand voltage can be improved.

The present invention relates to a photoelectric conversion deviceincluding, over a substrate, a photoelectric conversion layer having afirst semiconductor layer of one conductivity type, a secondsemiconductor layer, and a third semiconductor layer of an inverseconductivity type to the conductivity type of the first semiconductorlayer; a first electrode that comes in contact with the firstsemiconductor layer through an opening formed in the photoelectricconversion layer; an insulating layer formed so as to come in contactwith the third semiconductor layer of the photoelectric conversion layerand provided with an opening, which exposes the third semiconductorlayer; and a second electrode that comes in contact with the thirdsemiconductor layer through the opening formed in the insulating layer;where the third semiconductor layer is removed in a region that is notcovered with the first electrode, the insulating layer, and the secondelectrode of the photoelectric conversion layer.

In addition, the present invention relates to a method for manufacturinga photoelectric conversion device. The method for manufacturing aphotoelectric conversion device includes the steps of, over a substrate,forming a photoelectric conversion layer having a first semiconductorlayer of one conductivity type, a second semiconductor layer, and athird semiconductor layer of an inverse conductivity type to theconductivity type of the first semiconductor layer; forming a firstinsulating layer having a first opening over the photoelectricconversion layer; forming a second opening in the photoelectricconversion layer; forming a first electrode layer that comes in contactwith the first semiconductor layer through the second opening; andforming a second electrode layer that comes in contact with the thirdsemiconductor layer of the photoelectric conversion layer through thefirst opening; where the third semiconductor layer is removed in aregion that is not covered with the first electrode, the insulatinglayer, and the second electrode.

The present invention relates to a semiconductor device including, overa substrate, a photoelectric conversion element and a circuit for signalprocessing of the output value of the photoelectric conversion element.The photoelectric conversion element includes a photoelectric conversionlayer having a first semiconductor layer of one conductivity type, asecond semiconductor layer, and a third semiconductor layer of aninverse conductivity type to the conductivity type of the firstsemiconductor layer; a first electrode that comes in contact with thefirst semiconductor layer through an opening formed in the photoelectricconversion layer; an insulating layer formed so as to come in contactwith the third semiconductor layer of the photoelectric conversion layerand provided with an opening, which exposes the third semiconductorlayer; and a second electrode that comes in contact with the thirdsemiconductor layer through the opening formed in the insulating layer;where the third semiconductor layer is removed to in a region that isnot covered with the first electrode, the insulating layer, and thesecond electrode of the photoelectric conversion layer. The circuitincludes a plurality of thin film transistors, and each of the pluralityof thin film transistors has an island-like semiconductor regionincluding a source region, a drain region, and a channel formationregion; a gate insulating film; a gate electrode; a source electrodeelectrically connected to the source region; and a drain electrodeelectrically connected to the drain region.

The circuit is an amplifier circuit to amplify the output value of thephotoelectric conversion element.

The present invention relates to a photoelectric conversion deviceincluding, over a substrate, a first electrode; a photoelectricconversion layer having a first semiconductor film of one conductivitytype, a second semiconductor film, and a third semiconductor film of aninverse conductivity type to the conductivity type of the firstsemiconductor film; an insulating film covering the first electrode andthe photoelectric conversion layer; a second electrode that is formedover the insulating film and comes in contact with a part of the firstelectrode; and a third electrode that is formed over the insulating filmand comes in contact with a part of the third semiconductor film; wherethe photoelectric conversion layer overlaps and contacts with a part ofthe first electrode.

In the present invention, the first electrode is a transparentelectrode.

In the present invention, the transparent electrode includes any of anindium oxide-tin oxide alloy containing silicon, zinc oxide, tin oxide,indium oxide, or an indium oxide-zinc oxide alloy formed by using atarget in which indium oxide is mixed with 2 wt % or more to 20 wt % orless of zinc oxide.

In the present invention, the first electrode is a light-shieldingconductive film.

In the present invention, the light-shielding conductive film includesany of a single-layer film composed of an element selected fromtitanium, tungsten, tantalum, molybdenum, neodymium, cobalt, zirconium,zinc, ruthenium, rhodium, palladium, osmium, iridium, platinum,aluminum, gold, silver or copper, or an alloy material or a compoundmaterial containing the element as a main component; or a single-layerfilm composed of nitride thereof such as titanium nitride, tungstennitride, tantalum nitride or molybdenum nitride.

In the present invention, after the third semiconductor layer isremoved, a second insulating film having openings is formed, and throughthe openings, a first extraction electrode and a second extractionelectrode, which are connected to the first electrode layer and thesecond electrode layer respectively, are formed.

In the present invention, a conductive film is formed between thesubstrate and the first semiconductor layer.

In the present invention, the conductive film is a transparentconductive film.

In the present invention, a color filter is formed between the substrateand the first semiconductor layer.

In the present invention, each of the source electrode and the drainelectrode is a stacked film.

In the present invention, the stacked film is formed by stacking atitanium (Ti) film, an aluminum (Al) film containing the small amount ofsilicon (Si), and a titanium (Ti) film.

In the present invention, each of the source electrode and the drainelectrode is a single-layer film.

In the present invention, the single-layer film is a single-layer filmcomposed of an element selected from titanium (Ti), tungsten (W),tantalum (Ta), molybdenum (Mo), neodymium (Nd), cobalt (Co), zirconium(Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium(Os), iridium (Ir) or platinum (Pt), or an alloy material or a compoundmaterial containing the element as a main component; or a single-layerfilm composed of nitride thereof such as titanium nitride, tungstennitride, tantalum nitride or molybdenum nitride.

The present invention relates to a photoelectric conversion deviceincluding, over a substrate, a first electrode; a photoelectricconversion layer having a first to semiconductor film of oneconductivity type, a second semiconductor film, and a thirdsemiconductor film of an inverse conductivity type to the conductivitytype of the first semiconductor film; an insulating film covering thefirst electrode and the photoelectric conversion layer; a secondelectrode that is formed over the insulating film and comes in contactwith a part of the first electrode; and a third electrode that is formedover the insulating film and comes in contact with a part of the thirdsemiconductor film; where the photoelectric conversion layer overlapsand contacts with a part of the first electrode.

In the present invention, the first electrode is a transparentelectrode.

In the present invention, the transparent electrode includes any of anindium oxide-tin oxide alloy containing silicon, zinc oxide, tin oxide,indium oxide, or an indium oxide-zinc oxide alloy formed by using atarget in which indium oxide is mixed with 2 wt % or more to 20 wt % orless of zinc oxide.

In the present invention, the first electrode is a light-shieldingconductive film.

In the present invention, the light-shielding conductive film includesany of a single-layer film composed of an element selected fromtitanium, tungsten, tantalum, molybdenum, neodymium, cobalt, zirconium,zinc, ruthenium, rhodium, palladium, osmium, iridium, platinum,aluminum, gold, silver or copper, or an alloy material or a compoundmaterial containing the element as a main component; or a single-layerfilm composed of nitride thereof such as titanium nitride, tungstennitride, tantalum nitride or molybdenum nitride.

In the present invention, the substrate is a flexible substrate.

In the present invention, the substrate is a glass substrate.

In the present invention, the flexible substrate is one of apolyethylenenaphthalate (PEN) film, a polyethylene terephthalate (PET)film, and a polybutylene naphthalate (PBN) film.

In accordance with the present invention, a photo-sensor in whichelectrostatic discharge damage is suppressed can be manufactured. Inaddition, reliability of an electronic device in which such aphoto-sensor is incorporated can be enhanced.

Moreover, in a photo-sensor manufactured in accordance with the presentinvention, a wavelength of absorbed light can be closer to sensitivityof human eyes.

These and other objects, features and advantages of the presentinvention will become more apparent upon reading of the followingdetailed description along with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are views illustrating a manufacturing step of aphoto-sensor according to the present invention.

FIGS. 2A to 2C are views illustrating a manufacturing step of aphoto-sensor according to the present invention.

FIGS. 3A to 3C are views illustrating a manufacturing step of aphoto-sensor according to the present invention.

FIGS. 4A and 4B are views illustrating a manufacturing step of aphoto-sensor according to the present invention.

FIG. 5 is a top view of a photo-sensor according to the presentinvention.

FIG. 6 is a cross-sectional view of a conventional photo-sensor.

FIGS. 7A and 7B are views illustrating a manufacturing step of aphoto-sensor according to the present invention.

FIG. 8 is a view illustrating an example of an electronic device inwhich a photo-sensor according to the present invention is incorporated.

FIGS. 9A and 9B are views illustrating examples of electronic devices inwhich a photo-sensor according to the present invention is incorporated.

FIGS. 10A and 10B are views illustrating examples of electronic devicesin which a photo-sensor according to the present invention isincorporated.

FIG. 11 is a view illustrating an example of an electronic device inwhich a photo-sensor according to the present invention is incorporated.

FIG. 12 is a top view of a photo-sensor according to the presentinvention.

FIGS. 13A and 13B are views illustrating a manufacturing step of adevice in which a photo-sensor according to the present invention ismounted.

FIGS. 14A to 14C are views illustrating a manufacturing step of a devicein which a photo-sensor according to the present invention is mounted.

FIGS. 15A to 15C are views illustrating a manufacturing step of a devicein which a photo-sensor according to the present invention is mounted.

FIG. 16 is an equivalent circuit diagram of a photo-sensor for visiblelight in which a photo-sensor according to the present invention isincorporated.

FIG. 17 is an equivalent circuit diagram of a photo-sensor for visiblelight in which a photo-sensor according to the present invention isincorporated.

FIGS. 18A and 18B are views illustrating a manufacturing step of aphoto-sensor according to the present invention.

FIGS. 19A and 19B are views illustrating an example of an electronicdevice in which a photo-sensor according to the present invention isincorporated.

FIGS. 20A to 20 D are views illustrating a manufacturing step of adevice in which a photo-sensor according to the present invention ismounted.

FIG. 21 is a view illustrating a manufacturing step of a device in whicha photo-sensor according to the present invention is mounted.

DESCRIPTION OF THE INVENTION Embodiment

The present embodiment will be described with reference to FIGS. 1A to1B, 2A to 2C, and 3A to 3C.

First, over a substrate 101, a p-type semi-amorphous semiconductor filmis formed, for example, as a p-type semiconductor film 102. In thepresent embodiment, a flexible substrate is used as the substrate 101,and specifically, a film of to polyethylenenaphthalate (PEN) is used. Inaddition to polyethylenenaphthalate, a film of polyethyleneterephthalate (PET), polybutylene naphthalate (PBN) and the like may beused. Further, a glass substrate may also be used.

As the p-type semiconductor film 102, a semi-amorphous silicon filmcontaining an impurity element that belongs to Group 13 of the periodictable such as boron (B) is formed by plasma CVD.

A semi-amorphous semiconductor film includes a semiconductor that has anintermediate structure between an amorphous semiconductor and asemiconductor having a crystal structure (including a single crystal anda polycrystal). The semi-amorphous semiconductor has a third conditionthat is stable in terms of free energy, and it is a crystallinesubstance including a short range order and lattice distortion, thecrystal grain size of which can be 0.5 to 20 nm dispersed in anon-single crystal semiconductor film. In the semi-amorphoussemiconductor film, Raman spectrum is shifted to a wave number sidelower than 520 cm⁻¹, and diffraction peaks of (111) and (220) that aresaid to be caused by a crystal lattice of Si are observed in X-raydiffraction. In addition, at least 1 atomic % or more of hydrogen orhalogen is contained to terminate a dangling bond. In the presentspecification, the semiconductor film as described above is referred toas a semi-amorphous semiconductor (SAS) film for convenience. Moreover,a noble gas element such as helium, argon, krypton, or neon is containedto further promote lattice distortion so that stability is enhanced anda favorable semi-amorphous semiconductor film is obtained. It is to benoted that a semi-amorphous semiconductor film also includes amicro-crystalline semiconductor film (a microcrystal semiconductorfilm).

The SAS film can be obtained by glow discharge decomposition of a gascontaining silicon. SiH₄ is used as a typical gas containing silicon,and in addition, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiC₄, SiF₄, or the like canalso be used. The gas containing silicon may be diluted with hydrogen,or a gas in which one or more of noble gas elements of helium, argon,krypton and neon are added to hydrogen to easily form the SAS film. Itis preferable that the gas containing silicon be diluted in a 2-fold to1000-fold dilution factor range. Furthermore, a carbide gas such as CH₄or C₂H₆, a germanic gas such as GeH₄ or GeF₄, F₂ or the like may bemixed in the gas containing silicon to adjust an energy band width to be1.5 to 2.4 eV or 0.9 to 1.1 eV.

After the p-type semiconductor film 102 is formed, a semiconductor film103 which does not include an impurity imparting a conductivity type(intrinsic semiconductor film) and an n-type semiconductor film 104 areformed sequentially (FIG. 1A). Accordingly, a photoelectric conversionlayer including the p-type semiconductor film 102, the intrinsicsemiconductor film (also referred to as an i-type semiconductor film)103 and the n-type semiconductor film 104 is formed.

As the intrinsic semiconductor film 103, for example, a semi-amorphoussilicon film may be formed by plasma CVD. In addition, as the n-typesemiconductor film 104, a semi-amorphous silicon film containing animpurity element that belongs to Group 15 of the periodic table such asphosphorus (P) may be formed, or an impurity element that belongs toGroup 15 of the periodic table may be introduced after forming asemi-amorphous silicon film. It is to be noted that the amount of animpurity is controlled so that conductivity of the p-type semi-amorphoussemiconductor film 102 and the n-type semi-amorphous semiconductor film104 is 1 S/cm.

In addition, not only a semi-amorphous semiconductor film but also anamorphous semiconductor film may be used for the p-type semiconductorfilm 102, the intrinsic semiconductor film 103 and the n-typesemiconductor film 104.

In the present embodiment, the p-type semiconductor film, the intrinsicsemiconductor film and the n-type semiconductor film are stacked in thisorder. However, the p-type semiconductor film and the n-typesemiconductor film may be stacked in the reverse order, namely, then-type semiconductor film, the intrinsic semiconductor film and thep-type semiconductor film are stacked in this order.

Subsequently, an insulating film 106 having a groove 108 is formed byscreen printing or the like over the n-type semiconductor film 104 (FIG.1B). The groove 108 contacts with the n-type semiconductor film 104.Then, a groove 107 is formed in the insulating film 106, the n-typesemiconductor film 104, the intrinsic semiconductor film 103 and thep-type semiconductor film 102 by laser scribing (FIG. 2A). The groove107 is formed in the p-type semiconductor film 102, the intrinsicsemiconductor film 103 and the n-type semiconductor film 104, andcontacts with the p-type semiconductor film 102. In addition, the widthof the groove 107 is 50 μm to 300 μm.

After the groove 107 is formed, electrode layers 110 and 111 are formedwith a to conductive paste by ink jet (FIG. 2B). As the conductivepaste, a conductive paste containing a metal material such as silver(Ag), gold (Au), copper (Cu) or nickel (Ni), or a conductive carbonpaste can be used. In addition, the electrode layers 110 and 111 may beformed by screen printing.

Then, etching is conducted by using the electrode layers 110 and 111 andthe insulating film 106 as masks (FIG. 2C). By this etching, a part ofthe n-type semiconductor film 104, a part of the intrinsic semiconductorfilm 103, and a part of the insulating film 106 are etched to form anopening 120. This process removes the n-type semiconductor film 104, anda part of the intrinsic semiconductor film 103 is exposed. Therefore,the n-type semiconductor film 104 and the electrode layer 110 areelectrically separated so that the electrode layers 110 and 111 are notshort-circuited.

Subsequently, an insulating film 112 is formed to cover the electrodelayers 10 and 111, the insulating film 106, the n-type semiconductorfilm 104, the intrinsic semiconductor film 103 that is exposed by theetching, and the p-type semiconductor film 102 (FIG. 3A). Further,grooves 121 and 122 are formed in the insulating film 112 by laserscribing again (FIG. 3B), and extraction electrodes 113 and 114 areformed with a conductive paste (FIG. 3C). The same material may be usedfor the conductive paste as in the case of forming the electrode layers110 and 111.

As described above, one cell of a photo-sensor is formed. As for thephoto-sensor manufactured in the present embodiment, it is not necessaryto form a transparent electrode, since, among the p-type semiconductorfilm 102, the intrinsic semiconductor film 103 and the n-typesemiconductor film 104 which are a photoelectric conversion layer, thep-type semiconductor film 102 and the n-type semiconductor film 104substantially serve as an electrode.

In addition, in the photo-sensor according to the present invention, aregion 116 where the electrode layer 110 contacts with the p-typesemiconductor film 102 and a region 117 where the electrode layer 111contacts with the n-type semiconductor film 104 can be kept away interms of a distance. An electric current flows through the extractionelectrode 113, the electrode layer 110, the p-type semiconductor film102, the intrinsic semiconductor film 103, the n-type semiconductor film104, the electrode layer 111 and the extraction electrode 114. Asdescribed above, since the region where the electrode layer 110 contactswith the p-type semiconductor film 102 and the region where theelectrode layer 111 contacts with the n-type semiconductor film 104 arekept away in terms of a position so that an electric field is notconcentrated, and withstand voltagewithstand voltage to electrostaticdischarge damage can be improved.

FIG. 12 is a top view of the photo-sensor of FIG. 3C. It is to be notedthat the insulating film 112 is not illustrated. When a distance betweenthe electrode layers 110 and 111 is referred to as X₁ (μm), resistanceincreases when X₁ is large. Therefore, it is necessary to determine X₁in view of the resistance value of a whole element and its ability towithstand voltage that leads to electrostatic discharge damage. In otherwords, when X₁ is too small, resistance is lowered, and its ability towithstand voltage and, therefore, electrostatic discharge damage is alsolowered. On the other hand, when X₁ is too large, resistance of thewhole element increases too much, and it does not function as anelement.

In accordance with the present invention, a photo-sensor in whichelectrostatic discharge damage is suppressed can be manufactured; andthus, a high reliable product in which such a photo-sensor isincorporated can be obtained.

In addition, a semiconductor film used for a photoelectric conversionlayer can be used to serve as an electrode; and thus, a thickness of aphoto-sensor can be thinner than a conventional one.

Further, a transparent electrode that has been formed conventionally isnot formed, and a semiconductor film used for a photoelectric conversionlayer is used to serve as an electrode; and thus, a wavelength of lightthat is absorbed by the photo-sensor according to the present inventioncan be brought close to sensitivity of human eyes.

EXAMPLE 1

In the present example, examples of various electronic devices in whicha photo-sensor obtained by the present invention is incorporated will bedescribed. As an electronic device to which the present invention isapplied, a computer, a display, a cellular phone, a television and thelike are given. Specific examples of those electronic devices are shownin FIGS. 8, 9A and 9B, 10A and 10B, and 11, and 19.

FIG. 8 shows a cellular phone, which includes a main body (A) 601, amain body (B) 602, a chassis 603, operation keys 604, a sound inputportion 605, a sound output portion 606, a circuit substrate 607, adisplay panel (A) 608, a display panel (B) 609, a hinge 610, a lighttransmitting material portion 611, and a photo-sensor 612. The presentinvention can be applied to the photo-sensor 612.

The photo-sensor 612 detects light transmitted through the lighttransmitting material portion 611, and controls luminance of the displaypanel (A) 608 and the display panel (B) 609 depending on the illuminanceof the detected extraneous light, or controls illumination of theoperation keys 604 based on the illuminance obtained by the photo-sensor612. In this manner, current consumption of the cellular phone can besuppressed.

FIGS. 9A and 9B show other examples of a cellular phone. In FIGS. 9A and9B, reference numeral 621 denotes a main body; 622, a chassis; 623, adisplay panel; 624, operation keys; 625, a sound output portion; 626, asound input portion; and 627 and 628, photo-sensor portions.

In the cellular phone shown in FIG. 9A, luminance of the display panel623 and the operation keys 624 can be controlled by detecting extraneouslight by the photo-sensor portion 627 provided in the main body 621.

Furthermore, in the cellular phone shown in FIG. 9B, a photo-sensorportion 628 is provided inside the main body 621 in addition to thestructure of FIG. 9A. By the photo-sensor portion 628, luminance of backlight that is provided in the display panel 623 can also be detected.

FIG. 10A shows a computer, which includes a main body 631, a chassis632, a display portion 633, a key-board 634, an external connection port635, a pointing mouse 636 and the like.

In addition, FIG. 10B shows a display device such as a TV set. Thedisplay device includes a chassis 641, a support 642, a display portion643 and the like.

A detailed structure of the display portion 633 of the computer shown inFIG. 10A and the display portion 643 of the display device shown in FIG.10B, to which a liquid crystal panel is used, is shown in FIG. 11.

A liquid crystal panel 662 shown in FIG. 11 is built in the chassis 661,and includes substrates 651 a and 651 b, a liquid crystal layer 652interposed between the substrates 651 a and 651 b, polarizing filters653 a and 653 b, back light 654 and the like. In addition, aphoto-sensor portion 655 is formed in the chassis 661.

The photo-sensor portion 655 manufactured by using the present inventiondetects the amount of light from the back light 654, and the informationis fed back to adjust luminance of the liquid crystal panel 662.

FIGS. 19A and 19B are drawings illustrating an example in which thephoto-sensor according to the present invention is incorporated in acamera, for example, a digital camera. FIG. 19A is a perspective viewfrom the front side of the digital camera, and FIG. 19B is a perspectiveview from the back side thereof. In FIG. 19A, a digital camera isprovided with a release button 1301, a main switch 1302, a finder 1303,a flash portion 1304, a lens 1305, a barrel 1306, and a chassis 1307.

In addition, in FIG. 19B, a digital camera is provided with an eyepiecefinder 1311, a monitor 1312, and an operation button 1313.

When the release button 1301 is pushed down to the half point, a focusadjustment mechanism and an exposure adjustment mechanism are operated,and when the release button is pushed down to the lowest point, ashutter is opened.

By pushing down or rotating the main switch 1302, a power supply of thedigital camera is switched on or off.

The finder 1303 is a device located in the upper position of the lens1305, which is on the front side of the digital camera, for checking ashooting range and the focus point from the eyepiece finder 1311 shownin FIG. 19B.

The flash portion 1304 is located in the upper position on the frontside of the digital camera, from which, when the subject brightness isnot enough, auxiliary light is emitted at the same time as the releasebutton is pushed down and a shutter is opened.

The lens 1305 is located at the front of the digital camera, and formedby using a focusing lens, a zoom lens and the like. The lens forms aphotographic optical system with a shutter and a diaphragm which are notillustrated. In addition, behind the lens, an image sensor such as a CCD(Charge Coupled Device) is provided.

The barrel 1306 moves a lens position to adjust the focus of thefocusing lens, the zoom lens and the like. In shooting, the barrel isslid out to move the lens 1305 forward. Further, when carrying it, thelens 1305 is moved backward to be compact. It is to be noted that astructure is employed in the present example, in which the object can bephotographed by zoom by sliding out the barrel; however, a structure isnot limited thereto, and a structure may also be employed, in whichshooting can be conducted by zoom without sliding out the barrel due toa structure of a photographic optical system inside the chassis 1307.

The eyepiece finder 1311 is located in the upper position on the backside of the digital camera for looking through when checking a shootingrange and the focus point.

The operation button 1313 is a button for various functions provided onthe back side of the digital camera, and formed by a set up button, amenu button, a display button, a functional button, a selecting buttonand the like.

When the photo-sensor according to the present invention is incorporatedin the camera shown in FIGS. 19A and 19B, the photo-sensor can detectwhether light exists or not, and the light intensity; and thus, anexposure adjustment of a camera and the like can be conducted.

In addition, the photo-sensor according to the present invention canalso be applied to other electronic devices such as a projection TV anda navigation system. In other words, it can be applied to any electronicdevice as long as it needs to detect light.

EXAMPLE 2

In the present example, examples of providing an auxiliary electrodewill be described with reference to FIGS. 4A and 4B, and 5.

In FIG. 4A, reference numeral 201 denotes a substrate; 203, a p-typesemiconductor film; 205, an intrinsic semiconductor film; and 206, ann-type semiconductor film. In addition, 207 and 208 denote electrodelayers; 209 and 210, insulating films, and 211 and 212, extractionelectrodes.

The present example has a structure in which an auxiliary electrode 204is provided in addition to the structure of the embodiment. Theauxiliary electrode 204 may be formed by using a conductive film. In thepresent example, a transparent conductive film is used as the conductivefilm, and an indium oxide-tin oxide alloy containing silicon (Si) (alsoreferred to as indium tin oxide containing Si) is used as thetransparent conductive material. In addition to the indium oxide-tinoxide alloy containing Si, zinc oxide (ZnO), tin oxide (SnO₂), indiumoxide, a conductive film material formed by using a target in whichindium oxide is further mixed with 2 to 20 wt % of zinc oxide (ZnO) mayalso be used.

When an area of a light-receiving region can be kept sufficiently, theauxiliary electrode 204 may be formed by using a conductive film that isnot a transparent conductive film. As such a conductive film, asingle-layer film composed of an element selected from titanium (Ti),tungsten (W), tantalum (Ta), molybdenum (Mo), neodymium (Nd), cobalt(Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium(Pd), osmium (Os), iridium (Ir), platinum (Pt), aluminum (Al), gold(Au), silver (Ag) or copper (Cu), or an alloy material or a compoundmaterial containing the element as a main component; or a single-layerfilm composed of nitride thereof such as titanium nitride, tungstennitride, tantalum nitride or molybdenum nitride may be used.

When the auxiliary electrode 204 is formed, while resistance of a wholeelement is lowered, there is an advantage that electric resistance ofthe p-type semiconductor film 203 and the n-type semiconductor film 206can be the same by forming the auxiliary electrode 204 so as to come incontact with the p-type semiconductor film 203.

In addition, as shown in FIG. 4B, in the case of using the auxiliaryelectrode 204, etching can be conducted by using the auxiliary electrode204 as an etching stopper when the intrinsic semiconductor film 205 isetched for separating the electrode layers 207 and 208. Therefore, theintrinsic semiconductor film 205 can be etched until the auxiliaryelectrode 204 is exposed.

FIG. 5 is a top view of the photo-sensor of FIG. 4B. It is to be notedthat, in order to make a drawing clear, the insulating film 209 isindicated by a region surrounded by a dotted line and the insulatingfilm 210 is not illustrated. Further, grooves 221 and 222 correspond tothe grooves 107 and 108 of FIG. 1C.

When the distance between the auxiliary electrode 204 and the electrodelayer 208 is referred to as X₂ (μm), resistance increases when X₂ islarge. Therefore, it is necessary to determine X₂ in view of theresistance value of a whole element and withstand voltage toelectrostatic discharge damage. In other words, when X₂ is too small,resistance is lowered, and withstand voltage to electrostatic dischargedamage is also lowered. On the other hand, when X₂ is too large,resistance of the whole element increases too much, and it does notfunction as an element.

Furthermore, the present example can be applied to any descriptions ofthe Embodiment and the Example 1.

EXAMPLE 3

In the present example, examples of forming a color filter in thephoto-sensor according to the present invention will be described withreference to FIGS. 7A and 7B.

FIG. 7A shows a photo-sensor in which a color filter is formed in thephoto-sensor of FIG. 2C. In the photo-sensor of FIG. 7A, a substrate301, a p-type semiconductor film 302, an intrinsic semiconductor film303, an n-type semiconductor film 304, an insulating film 305, electrodelayers 306 and 307, an insulating film 308, extraction electrodes 309and 310, and a color filter 311 are formed.

By providing the color filter 311, each light of red (R), green (G) andblue (B) can be absorbed selectively.

In addition, FIG. 7B shows an example in which a color filter is formedbetween a substrate and a photoelectric conversion layer.

In FIG. 7B, reference numeral 321 denotes a substrate; 322, a p-typesemiconductor film; 323, an intrinsic semiconductor film; 324, an n-typesemiconductor film; 325 and 328, insulating films; 326 and 327,electrode layers; 329 and 330, extraction electrodes; 331, a colorfilter; and 332, a passivation film. The passivation film 332 may beformed by using the same material as the insulating film 325.

In the structure shown in FIG. 7B, even when light enters obliquely froma substrate side, the light can transmit the color filter; and thus, theincident light can be used effectively.

Furthermore, the present example can be applied to any descriptions ofthe Embodiment and the Examples 1 and 2.

EXAMPLE 4

In the present example, a semiconductor device using the photoelectricconversion device according to the present invention will be describedwith reference to FIGS. 13A and 13B, 14A and 14B, 15A to 15C, 16, 17,and 20A to 20 D.

In FIG. 13A, as an example of a semiconductor device using thephotoelectric conversion device according to the present invention, anexample of a photo-sensor chip (2.0 mm×1.5 mm) for visible light withtwo terminals is shown. In FIG. 13A, reference numeral 710 denotes asubstrate; 712, a base insulating film; and 713, a gate insulating film.Since received light transmits the substrate 710, the base insulatingfilm 712 and the gate insulating film 713, it is desirable to use ahighly light-transmitting material for all of them.

A PIN-type photoelectric conversion element 725 may be formed based onthe description of the embodiment, and the present example shows a briefdescription thereof. The photoelectric conversion element 725 accordingto the present example includes a wiring 719, a protective electrode718, a p-type semiconductor layer 721 p, an n-type semiconductor layer721 n, an intrinsic (i-type) semiconductor layer 7211 interposed betweenthe p-type semiconductor layer 721 p and the n-type semiconductor layer721 n, which are the photoelectric conversion layer 725, and a terminalelectrode 726.

The wiring 719 has a stacked structure of a refractory metal film and alow resistance metal film (such as an aluminum alloy or pure aluminum).Here, the wiring 719 has a three-layer structure in which a titaniumfilm (Ti film), an aluminum film (Al film) and a Ti film are stackedsequentially. The protective electrode 718 is formed to cover the wiring719.

When the photoelectric conversion layer 721 is etched, the wiring 719 isprotected by the protective electrode 718 covering the wiring 719. Amaterial for the protective electrode 718 is preferably a conductivematerial in which an etching rate is lower than in the photoelectricconversion layer with respect to an etching gas (or an etchant) for thephotoelectric conversion layer 721. In addition, a material for theprotective electrode 718 is preferably a conductive material which doesnot react with the photoelectric conversion layer 721 to be an alloy.

In addition, a circuit for signal processing of the output value of thePIN-type photoelectric conversion element 725 is provided. In thepresent example, an amplifier circuit is provided as the circuit forsignal processing of the output value of the PIN-type photoelectricconversion element 725. The amplifier circuit provided over the samesubstrate to amplify the output value of the photoelectric conversionelement 725 is formed by a current mirror circuit 732 by n-channel thinfilm transistors (Thin Film Transistor (TFT)) 730 and 731 (FIG. 13A).

In addition, an equivalent circuit diagram of a photo-sensor for visiblelight with two terminals is shown in FIG. 13B. FIG. 13B is an equivalentcircuit diagram using an n-channel TFT; however, only a p-channel TFTmay also be used instead of the n-channel TFT.

Two TFTs are illustrated in FIG. 13A. However, for example, in order toincrease the output value by five times, 2 pieces of the n-channel TFT730 (channel-length (L) and channel width (W) are 8 μm and 50 μm,respectively) and 10 pieces of the n-channel TFT 731 (channel-length (L)and channel width (W) are 8 μm and 50 μm, respectively) may be provided.

Further, in order to increase the output value by m times, a piece ofthe n-channel TFT 730 and m pieces of the n-channel TFT 731 may beprovided. Specifically, an example of providing a piece of the n-channelTFT 730 and 100 pieces of the n-channel TFT 731 in order to increase theoutput value by 100 times is shown in FIG. 16. It is to be noted thatthe same reference numerals as in FIGS. 13A and 13B, and 14A to 14C areused for the same portions in FIG. 16. In FIG. 16, the n-channel TFT 731includes 100 pieces of n-channel TFT 731 a, 731 b, 731 c, 731 d, . . . .In this manner, a photoelectric current generated in the photoelectricconversion element 725 is amplified by 100 times and outputted.

FIG. 17 is an equivalent circuit diagram in the case where the amplifiercircuit is formed by using a p-channel TFT. In FIG. 17, terminalelectrodes 726 and 753 are the same as in FIG. 13B, which may beconnected to a photoelectric conversion element 825 and p-channel TFTs830 and 831 respectively. The p-channel TFT 830 is electricallyconnected to an electrode on the anode side of the photoelectricconversion element 825. In the photoelectric conversion element 825, ann-type semiconductor layer, an intrinsic semiconductor layer (an i-typesemiconductor layer), and a p-type semiconductor layer are stacked inthis order over a second electrode (an electrode on the anode side)connected to the p-channel TFT 830; and then, a first electrode (anelectrode on the cathode side) may be formed. In addition, aphotoelectric conversion element having a reverse stacking order mayalso used, in which a p-type semiconductor layer, an intrinsicsemiconductor layer (an i-type semiconductor layer) and an n-typesemiconductor layer are stacked in this order over a first electrode (anelectrode on the cathode side); and then, a second electrode (anelectrode on the anode side) connected to the p-channel TFT 830 isformed, and a terminal electrode on the cathode side connected to thefirst electrode may be formed.

An amplifier circuit to further amplify the output value may be formedby using an operational amplifier in which an n-channel TFT and ap-channel TFT are appropriately combined; however, the amplifier circuithas five terminals. Meanwhile, the number of power supplies can bereduced, and the amplifier circuit has four terminals by forming theamplifier circuit by using an operational amplifier and a level shifter.

It is to be noted that the amplifier circuit to amplify the output valueis formed in the present example; however, a circuit for converting theoutput value into another output form or the like may also bemanufactured instead of the amplifier circuit, if necessary.

In addition, in FIG. 13A, an example of a top gate TFT in which then-channel TFTs 730 and 731 include one channel formation region(referred to as “single gate structure” in the present specification) isshown; however, a structure including a plurality of channel formationregions may also be employed to reduce variation in ON current value.Further, the n-channel TFTs 730 and 731 may be provided with alow-concentration drain (Lightly Doped Drain (LDD)) region to reduce theOFF current value. An LDD region is a region doped with an impurityelement at a low concentration between the channel formation region anda source region or drain region that is formed by adding an impurityelement at a high concentration. When an LDD region is provided, thereis an advantageous effect that an electric field in the vicinity of adrain region is relieved, thereby preventing deterioration due to hotcarrier injection. In addition, in order to prevent deterioration in ONcurrent value due to a hot carrier, the n-channel TFTs 730 and 731 mayhave a structure in which an LDD region is stacked over a gate electrodewith a gate insulating film interposed therebetween (referred to as“GOLD (Gate-drain Overlapped LDD) structure” in the presentspecification).

In the case of using the GOLD structure, the advantageous effect ofrelieving an electric field in the vicinity of a drain region, therebypreventing deterioration due to hot carrier injection is more enhancedthan in the case where the LDD region does not overlap with the gateelectrode. It is effective to employ such a GOLD structure in order toprevent a deterioration phenomenon since an electric field intensity inthe vicinity of a drain region is relieved, thereby preventing hotcarrier injection.

In addition, the wiring 714 is a wiring that is connected to the wiring719, and extends to the upper portion of the channel formation region ofthe TFT 730 of the amplifier circuit to serve as a gate electrode.

In addition, the wiring 715 is a wiring that is connected to the n-typesemiconductor layer 721 n and further connected to a drain wiring (alsoreferred to as a drain electrode) or a source wiring (also referred toas a source electrode) of the TFT 731. Further, reference numerals 716and 717 denote insulating films; and 720, a connecting electrode. Sincereceived light transmits the insulating films 716 and 717, it isdesirable to use a highly light-transmitting material for all of them. Asilicon oxide film (SiOx film) formed by CVD is preferably used for theinsulating film 717. When a silicon oxide film formed by CVD is used forthe insulating film 717, anchoring intensity is improved.

In addition, a terminal electrode 750 is formed in the same step as thewirings 714 and 715, and a terminal electrode 751 is formed in the samestep as the wirings 719 and 720.

In addition, a terminal electrode 726 is connected to the n-typesemiconductor layer 721 n, and mounted over an electrode 761 of aprinted wiring board 760 with solder 764. In addition, a terminalelectrode 753 is formed in the same step as the terminal electrode 726,and mounted over an electrode 762 of the printed wiring board 760 withsolder 763.

Hereinafter, manufacturing steps to obtain the structure as describedabove will be described with reference to FIGS. 14A to 14C and 20A to20D.

First, an element is formed over a substrate (a first substrate 710).Here, AN 100 that is one of glass substrates is used as the substrate710.

Subsequently, a silicon oxide film containing nitrogen which serves as abase insulating film 712 (100 nm thick) is formed by plasma CVD, and asemiconductor film such as an amorphous silicon film containing hydrogen(54 nm thick) is stacked thereover without being exposed to atmosphericair. In addition, a silicon oxide film, a silicon nitride film and asilicon oxide film containing nitrogen may be stacked to form the baseinsulating film 712. Specifically, a silicon nitride film containingoxygen of 50 nm, and further, a silicon oxide film containing nitrogenof 100 nm may be staked to form the base insulating film 712. It is tobe noted that the silicon oxide film containing nitrogen or the siliconnitride film serves as a blocking layer for preventing diffusion of animpurity such as an alkali metal from a glass substrate.

Then, the amorphous silicon film is crystallized by using a knowntechnique (such as a solid-phase growth method, a laser crystallizationmethod, or a crystallization method using a catalyst metal) to form asemiconductor film having a crystal structure (a crystallinesemiconductor film), for example, a polycrystal silicon film. Here, apolycrystal silicon film is obtained by a crystallization method using acatalyst element. A nickel acetate solution containing nickel of 10 ppmby weight is applied by a spinner. It is to be noted that a nickelelement may be dispersed over the entire surface by sputtering insteadof applying. Then, a heat treatment is conducted for crystallization toform a semiconductor film having a crystal structure (here, apolycrystal silicon film). Here, a polycrystal silicon film is obtainedby a heat treatment for crystallization (at 550° C. for 4 hours) afterthe heat treatment (at 550° C. for one hour).

Next, an oxide film over the surface of the polycrystal silicon film isremoved by a dilute hydrofluoric acid or the like. Thereafter,irradiation of laser light (XeCl: wavelength of 308 nm) for raising adegree of crystallization and repairing a defect left in a crystal grainis performed in an atmospheric air or in an oxygen atmosphere.

Excimer laser light of a wavelength of 400 nm or less, or the secondharmonic or the third harmonic of a YAG laser is used for the laserlight. Here, pulsed laser light having a repetition frequency ofapproximately 10 to 1000 Hz is used. The laser light is condensed to 100to 500 mJ/cm² by an optical system, and irradiation is performed with anoverlap rate of 90 to 95%, thereby scanning the silicon film surface. Inthe present example, the irradiation of the laser light is performed inan atmospheric air with a repetition frequency of 30 Hz and energydensity of 470 mJ/cm².

It is to be noted that an oxide film is formed over the surface by thelaser light irradiation since the irradiation is conducted in anatmospheric air or in an oxygen atmosphere. Although an example of usingthe pulsed laser is shown in the present example, a continuous wavelaser may also be used. For crystallization of a semiconductor film, itis preferable that the second harmonic to the fourth harmonic of thefundamental wave be applied by using a continuous wave solid state laserin order to obtain a crystal of a large grain size. As a typicalexample, the second harmonic (532 nm) or the third harmonic (355 nm) ofan Nd:YVO₄ laser (fundamental wave of 1064 nm) may be applied.

In the case of using a continuous wave laser, laser light emitted fromthe continuous wave type YVO₄ laser of 10 W output is converted intoharmonics by using a non-linear optical element. Further, a method ofemitting harmonics by applying a YVO₄ crystal and the non-linear opticalelement into a resonator can also be given. Then, the laser light havinga rectangular shape or an elliptical shape on an irradiated face ispreferably formed by an optical system, and an object is irradiated withthis laser light. At this time, the energy density of approximately 0.01to 100 MW/cm² (preferably, 0.1 to 10 MW/cm²) is required. Thesemiconductor film may be moved at approximately 10 to 2000 cm/s raterelatively with respect to the laser light so as to be irradiated.

Then, in addition to the oxide film formed by the laser lightirradiation, a barrier layer made of an oxide film having a thickness of1 to 5 nm in total is formed by treating the surface with ozone waterfor 120 seconds. The barrier layer is formed in order to remove acatalyst element, which is added for crystallization, such as nickel(Ni) from the film. Although the barrier layer is formed by using ozonewater here, a barrier layer may also be formed by depositing an oxidefilm of approximately 1 to 10 am thick by using a method of oxidizing asurface of a semiconductor film having a crystal structure by UV-rayirradiation in an oxygen atmosphere, a method of oxidizing a surface ofa semiconductor film having a crystal structure by an oxygen plasmatreatment, plasma CVD, sputtering, evaporation or the like. In addition,before forming the barrier layer, the oxide film formed by laser lightirradiation may be removed.

Then, over the barrier layer, an amorphous silicon film containing anargon element is formed to be 10 nm to 400 nm thick, for example 100 nmthick here, by sputtering to serve as a gettering site. Here, theamorphous silicon film containing an argon element is formed in anatmosphere containing argon using a silicon target. When plasma CVD isused to form the amorphous silicon film containing an argon element, thedeposition condition is as follows: a flow ratio of monosilane to argon(SiH₄:Ar) is set to be 1:99; deposition pressure is set to be 6.665 Pa;the RF power density is set to be 0.087 W/cm²; a deposition temperatureis set to be 350° C.

Thereafter, a furnace heated to 650° C. is used for a heat treatment forthree minutes to remove a catalyst element (gettering). By thistreatment, the catalyst element concentration in the semiconductor filmhaving a crystal structure is reduced. A lamp annealing apparatus mayalso be used instead of the furnace.

Subsequently, the amorphous silicon film containing an argon element,which is a gettering site, is selectively removed with the barrier layeras an etching stopper, and then, the barrier layer is selectivelyremoved by dilute hydrofluoric acid. It is to be noted that there is atendency that nickel is likely to move to a region with a high oxygenconcentration in gettering, and thus, it is desirable that the barrierlayer made of the oxide film be removed after gettering.

It is to be noted that, in the case where crystallization of asemiconductor film using a catalytic element is not performed, the abovedescribed steps such as the formation of the barrier layer, theformation of the gettering site, the heat treatment for gettering, theremoval of the gettering site, and the removal of the barrier layer arenot required.

Then, after a thin oxide film is formed with ozone water over thesurface of the obtained semiconductor film having a crystal structure(such as a crystalline silicon film), a mask made of resist is formed byusing a first photomask, and an etching treatment is conducted to obtaina desired shape, thereby forming semiconductor films 741 and 742separated in island shapes (referred to as “island-like semiconductorregion” in the present specification) (refer to FIG. 20A). After formingthe island-like semiconductor regions 741 and 742, the mask made ofresist is removed.

Subsequently, if necessary, doping of the very small amount of animpurity element (boron or phosphor) is performed to control thethreshold value of a TFT. Here, ion doping is used, in which diborane(B₂H₆) is not separated by mass but excited by plasma.

Next, the oxide film is removed with an etchant containing hydrofluoricacid, and at the same time, the surface of the island-like semiconductorregion is washed. Thereafter, an insulating film containing silicon as amain component, which serves as a gate insulating film 713, is formed.Here, a silicon oxide film containing nitrogen (composition ratio:Si=32%, 0=59%, N=7%, H=2%) is formed to have a thickness of 115 nm byplasma CVD.

Then, after a metal film is formed over the gate insulating film 713, asecond photomask is used to form gate electrodes 744 and 745, wirings714 and 715, and a terminal electrode 750 (refer to FIG. 20B). Forexample, as the metal film, a film which is formed by stacking tantalumnitride (TaN) and tungsten (W) to be 30 nm and 370 nm respectively isused.

In addition to the above described materials, as the gate electrodes 744and 745, the wirings 714 and 715 and the terminal electrode 750, asingle-layer film composed of an element selected from titanium (Ti),tungsten (W), tantalum (Ta), molybdenum (Mo), neodymium (Nd), cobalt(Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium(Pd), osmium (Os), iridium (Ir), platinum (Pt), aluminum (Al), gold(Au), silver (Ag) or copper (Cu), or an alloy material or a compoundmaterial containing the element as a main component; or a single-layerfilm composed of nitride thereof such as titanium nitride, tungstennitride, tantalum nitride or molybdenum nitride can be used.

Then, doping to the island-like semiconductor regions 741 and 742 isperformed to form a source region or drain region 747 of the TFT 730 anda source region or drain region 748 of the TFT 731 (refer to FIG. 20C).In addition, in the island-like semiconductor region 741 of the TFT 730,a channel formation region is formed between a source region and a drainregion, and then, in the island-like semiconductor region 742 of the TFT731, a channel formation region is formed between a source region and adrain region.

Subsequently, after a first interlayer insulating film containingsilicon oxide film (not illustrated) is formed to be 50 nm by CVD, astep for an activation treatment of an impurity element added to eachisland-like semiconductor region is conducted. The activation step isconducted by rapid thermal annealing (RTA method) using a lamp lightsource, a method of irradiation of a YAG laser or an excimer laser fromthe back side, a heat treatment using a furnace, or a method which is acombination of the foregoing methods.

Next, a second interlayer insulating film 716 including a siliconnitride film containing hydrogen and oxygen is formed to have a filmthickness of, e.g. 10 nm.

Subsequently, a third interlayer insulating film 717 made of aninsulator material is formed over the second interlayer insulating film716 (refer to FIG. 20D). An insulating film obtained by CVD can be usedfor the third interlayer insulating film 717. In the present example, inorder to improve adhesiveness, a silicon oxide film containing nitrogenis formed to have a film thickness of 900 nm as the third interlayerinsulating film 717.

Then, a heat treatment (a heat treatment at 300 to 550° C. for 1 to 12hours, for example, at 410° C. for one hour in a nitrogen atmosphere) isconducted to hydrogenate the island-like semiconductor film. This stepis conducted to terminate a dangling bond in the island-likesemiconductor film by hydrogen contained in the second interlayerinsulating film 716. The island-like semiconductor film can behydrogenated regardless of whether or not the gate insulating film 713is formed.

In addition, as the third interlayer insulating film 717, an insulatingfilm using siloxane and a stacked structure thereof can also be used.Siloxane is composed by a skeleton structure of a bond of silicon (Si)and oxygen (O). As a substituent, a compound containing at leasthydrogen (such as an alkyl group or an aromatic hydrocarbon) is used.Fluorine may also be used as a substituent. Moreover, a compoundcontaining at least hydrogen and fluorine may be used as a substituent.

When an insulating film using siloxane and a stacked structure thereofare used as the third interlayer insulating film 717, after forming thesecond interlayer insulating film 716, a heat treatment forhydrogenating the island-like semiconductor film may be conducted, andthen, the third interlayer insulating film 717 may be formed.

Then, a mask made of resist is formed by using a third photomask, andthe first interlayer insulating film, the second interlayer insulatingfilm 716, and the third interlayer insulating film 717, and the gateinsulating film 713 are selectively etched to form a contact hole. Then,the mask made of resist is removed.

It is to be noted that the third interlayer insulating film 717 may beformed if necessary. When the third interlayer insulating film 717 isnot formed, after forming the second interlayer insulating film 716, thefirst interlayer insulating film, the second interlayer insulating film716, and the gate insulating film 713 are selectively etched to form acontact hole.

Subsequently, after forming a metal stacked film by sputtering, a maskmade of resist is formed by using a fourth photomask, and then, themetal film is selectively etched to form the wiring 719, the connectingelectrode 720, the terminal electrode 751, a source electrode or drainelectrode 771 of the TFT 730, and a source electrode or drain electrode772 of the TFT 731. Then, the mask made of resist is removed. It is tobe noted that the metal stacked film according to the present examplehas a stacked structure of three layers of a Ti film of 100 nm, an Alfilm containing the small amount of Si of 350 nm, and a Ti film of 100nm.

In the above-mentioned step, the top gate TFTs 730 and 731 using apolycrystal silicon film can be manufactured.

Then, after a conductive metal film (such as titanium (Ti) or molybdenum(Mo)) is formed, which is not likely to react with a photoelectricconversion layer that is formed later (typically, amorphous silicon) tobe an alloy, a mask made of resist is formed by using a fifth photomask,and the conductive metal film is selectively etched to form theprotective electrode 718 covering the wiring 719 (FIG. 14A). A Ti filmof 200 nm thick obtained by sputtering is used here. Similarly, theconnecting electrode 720, the terminal electrode 751, and the sourceelectrode or drain electrode of the TFT are also covered with theconductive metal film. Therefore, the conductive metal film also coversa side face where an Al film which is a second layer in the electrode isexposed, thereby preventing diffusion of an aluminum atom into thephotoelectric conversion layer.

Subsequently, the photoelectric conversion layer 721 is formed. The tophotoelectric conversion layer 721 is formed based on the descriptionsof the Embodiment and the Examples 1 to 3.

Then, a sealing layer 724 including an insulator material (for example,an inorganic insulating film containing silicon) is formed to have athickness of 1 μm to 30 μm over the entire surface, and a state of FIG.14B is obtained. Here, a silicon oxide film containing nitrogen of 1 μmthick is formed by CVD as the insulator material film. It is intendedthat adhesiveness be improved by using the insulating film formed byCVD.

Next, after the sealing layer 724 is etched to provide an opening, theterminal electrodes 726 and 753 are formed by sputtering. The terminalelectrodes 726 and 753 are made of a stacked film of a titanium film (Tifilm, 100 nm), a nickel film (Ni film, 300 nm), and a gold film (Aufilm, 50 nm). The anchoring intensity of the terminal electrodes 726 and753 obtained as described above is more than 5 N, which is a sufficientanchoring intensity for a terminal electrode.

In the above described steps, the terminal electrodes 726 and 753 thatcan be connected with solder are formed, and a structure shown in FIG.14C is obtained.

Subsequently, a plurality of photo-sensor chips are cut out by cuttingthe substrate into pieces. A large number of photo-sensor chips (2mm×1.5 mm) can be manufactured from one piece of large-area substrate(for example, 600 cm×720 cm).

A cross-sectional view (side view) of one piece of photo-sensor chip (2mm×1.5 mm) that is cut out is shown in FIG. 15A, a bottom view thereofis shown in FIG. 15B, and a top view thereof is shown in FIG. 15C. InFIGS. 15A to 15C, the same reference numerals as in FIGS. 13A and 13B,and 14A to 14C are used for the same portions. It is to be noted that,in FIG. 15A, a film thickness of the substrate 710, an element formationregion 800, the terminal electrodes 726 and 753 in total is 0.8±0.05 mm.

In addition, in order to make the total film thickness of thephoto-sensor chip thinner, a plurality of photo-sensor chips may be cutout by cutting the substrate into pieces using a dicer after thesubstrate 710 is ground and thinned by a CMP treatment or the like.

In FIG. 15B, the electrode size of one of the terminal electrodes 726and 753 is 0.6 mm×1.1 mm, and the electrode interval is 0.4 mm. Inaddition, in FIG. 15C, the area of a light receiving portion 801 isalmost the same as the area of the second electrode, that is, 1.57 mm².Further, an amplifier circuit portion 802 is provided with approximately100 TFTs.

Finally, the obtained photo-sensor chip is mounted on the mounting sideof the printed wiring board 760. Solder 764 and 763 is used forconnecting the terminal electrode 726 to the electrode 761, and theterminal electrode 753 to the electrode 762, respectively. The solder isformed in advance by screen printing or the like over the electrodes 761and 762 of the printed wiring board 760, and the solder and the terminalelectrode are made in an abutted state to conduct mounting by a reflowsoldering treatment. The reflow soldering treatment is conducted, forexample, at approximately 225° C. to 265° C. for about 10 seconds in aninert gas atmosphere. Further, in addition to the solder, a bump made ofa metal (such as gold or silver) or a bump made of a conductive resin orthe like can be used. In addition, lead-free solder may also be used formounting in consideration of an environmental problem.

FIG. 14A shows the photo-sensor chip mounted through the above-describedsteps. In the photo-sensor according to the present invention (aphoto-sensor integrated with a circuit and provided with an amplifiercircuit capable of increasing the output value by 100 times), aphotoelectric current of approximately 10 μA can be obtained atilluminance of 100 lux. In addition, in the photo-sensor according tothe present invention, a sensitivity wavelength range is 350 to 750 μm,and a peak sensitivity wavelength is 580 nm. Further, a dark current(Vr=5V) is 1000 pA.

It is to be noted that the present example can be combined with anydescriptions of the Embodiment and the Examples 1 to 3.

EXAMPLE 5

In the present example, examples of a photo-sensor provided with anauxiliary electrode, which are different from the Example 2, will bedescribed with reference to FIGS. 18A and 18B.

A photo-sensor shown in FIG. 18A includes an auxiliary electrode 902, ap-type semiconductor film 903, an intrinsic semiconductor film 904, ann-type semiconductor film 905, a first insulating film 906, a secondinsulating film 907, electrode layers 911 and 912, and extractionelectrodes 913 and 914 over a substrate 901.

Manufacturing steps of the photo-sensor in the present example will bedescribed hereinafter. First, the auxiliary electrode 902 is formed byusing a transparent conductive film over the substrate 901. In thepresent example, an indium oxide-tin oxide alloy containing silicon (Si)(also referred to as indium tin oxide containing Si) is used as thetransparent conductive material. In addition to the indium oxide-tinoxide alloy containing Si, zinc oxide (ZnO), tin oxide (SnO₂), indiumoxide, an indium oxide-zinc oxide alloy formed by using a target inwhich indium oxide is mixed with 2 to 20 wt % of zinc oxide (ZnO) mayalso be used.

When an area of a light-receiving region can be kept sufficiently, theauxiliary electrode 902 may be formed by using a conductive film that isnot a transparent conductive film, for example, a light shieldingconductive film. As such a conductive film, a single-layer film composedof an element selected from titanium (Ti), tungsten (W), tantalum (Ta),molybdenum (Mo), neodymium (Nd), cobalt (Co), zirconium (Zr), zinc (Zn),ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir),platinum (Pt), aluminum (Al), gold (Au), silver (Ag) or copper (Cu), oran alloy material or a compound material containing the element as amain component; or a single-layer film composed of nitride thereof suchas titanium nitride, tungsten nitride, tantalum nitride or molybdenumnitride may be used.

After the auxiliary electrode 902 is formed, a photoelectric conversionlayer including the p-type semiconductor film 903, the intrinsicsemiconductor film 904 and the n-type semiconductor film 905 is formed.The photoelectric conversion layer including the p-type semiconductorfilm 903, the intrinsic semiconductor film 904 and the n-typesemiconductor film 905 may have a stacked structure of the reverseorder, namely, the n-type semiconductor film, the intrinsicsemiconductor film and the p-type semiconductor film are stacked in thisorder to form a photoelectric conversion layer.

In the present example, for example, a p-type semi-amorphoussemiconductor film is formed as the p-type semiconductor film 903. Asthe p-type semi-amorphous semiconductor film, a semi-amorphous siliconfilm containing an impurity element that belongs to Group 13 of theperiodic table such as boron (B) is formed by plasma CVD.

After the p-type semiconductor film 903 is formed, the semiconductorfilm (intrinsic semiconductor film) 904 which does not includeimpurities imparting a conductivity type and the n-type semiconductorfilm 905 are formed sequentially.

As the intrinsic semiconductor film 904, for example, a semi-amorphoussilicon film may be formed by plasma CVD. In addition, as the n-typesemiconductor film 905, a semi-amorphous silicon film containing animpurity element that belongs to Group 15 of the periodic table such asphosphorus (P) may be formed, or an impurity element that belongs toGroup 15 of the periodic table may be introduced after forming thesemi-amorphous silicon film. It is to be noted that the amount of animpurity is controlled so that conductivity of the p-type semi-amorphoussemiconductor film 903 and the n-type semi-amorphous semiconductor film905 is 1 S/cm.

In addition, not only a semi-amorphous semiconductor film but also anamorphous semiconductor film may be used for the p-type semiconductorfilm 903, the intrinsic semiconductor film 904 and the n-typesemiconductor film 905.

Next, the first insulating film 906 is formed over the n-typesemiconductor film 905 by screen printing or the like.

Then, the p-type semiconductor film 903, the intrinsic semiconductorfilm 904, the n-type semiconductor film 905 and the first insulatingfilm 906 are etched to expose a part of the auxiliary electrode 902. Inother words, it is a state that the p-type semiconductor film 903, theintrinsic semiconductor film 904, the n-type semiconductor film 905 andthe first insulating film 906 are stacked over the other part of theauxiliary electrode 902. The photoelectric conversion layer includingthe p-type semiconductor film 903, the intrinsic semiconductor film 904and the n-type semiconductor film 905 overlaps and contacts with theother part of the auxiliary electrode 902. Thereafter, the secondinsulating film 907 is formed to cover the auxiliary electrode 902, thep-type semiconductor film 903, the intrinsic semiconductor film 904, then-type semiconductor film 905 and the first insulating film 906.

Subsequently, a contact hole (groove) is formed in the first insulatingfilm 906 and the second insulating film 907, and then, the electrodelayers 911 and 912 are formed with a conductive paste by screenprinting. As the conductive paste, a conductive paste containing a metalmaterial such as silver (Ag), gold (Au), copper (Cu) or nickel (Ni), ora conductive carbon paste can be used. In addition, the electrode layers911 and 912 may be formed by ink jet. That is to say, the electrodelayer 911 is not connected to the entire surface of the auxiliaryelectrode 902, but connected in contact with a part of the auxiliaryelectrode 902. In addition, the electrode layer 912 is not connected tothe entire surface of the n-type semiconductor film 905, but connectedin contact with a part of the n-type semiconductor film 905.

If necessary, the extraction electrodes 913 and 914 are formed so as tobe in contact with the electrode layers 911 and 912 (FIG. 18A). Theextraction electrodes 913 and 914 are formed in the same manner as theelectrode layers 911 and 912.

FIG. 18B shows an example of forming an electrode in the upper positionof the photoelectric conversion layer of the photo-sensor of FIG. 18A.In FIG. 18B, an auxiliary electrode 932 is formed over a substrate 931,and a photoelectric conversion layer including a p-type semiconductorfilm 933, an intrinsic semiconductor film 934 and an n-typesemiconductor film 935 overlaps and contacts with a part of theauxiliary electrode 932.

Then, an upper electrode 936 is formed over the n-type semiconductorfilm 935 overlapping with a part of the n-type semiconductor film 935.The upper electrode 936 is formed by the same material as the auxiliaryelectrode 932.

Further, a first insulating film 937 and a second insulating film 938are formed, and a contact hole (groove) is formed. Then, electrodelayers 941 and 942 are formed. If necessary, extraction electrodes 943and 944 are formed. The first insulating film 937, the second insulatingfilm 938, the electrode layers 941 and 942, and the extractionelectrodes 943 and 944 are formed by the same material and in the samemanufacturing step as in FIG. 18A.

When the upper electrode 936 is formed, resistance of a wholephoto-sensor is lowered; however, the resistance value of thephoto-sensor can be controlled by the distance between the auxiliaryelectrode 932 and the upper electrode 936.

The length of a region where the auxiliary electrode 932 overlaps withthe p-type semiconductor film 933 is referred to as X₃ (=100 μm), andthe distance between an end portion of the auxiliary electrode 932 andan end portion of the upper electrode 936 is referred to as X₄.Withstand voltage (V) and series resistance (Ω) in the case of settingX₄ to be 0 μm, 100 μm and 200 μm, respectively, are indicated in thetable 1.

TABLE 1 X₄ (μm) Withstand voltage (V) Series resistance (Ω) 0 100~20025k 100  500~1000 40k 200 1000~1500 55k

As indicated in the table 1, even when the resistance value of thephoto-sensor is lowered by forming the upper electrode 936, theresistance value of a whole element can be increased by changing thedistance between the upper electrode 936 and the auxiliary electrode932.

It is to be noted that the present example can be combined with anydescriptions of the Embodiment and the Examples 1 to 4, if necessary.

EXAMPLE 6

In the present example, as for a photo-sensor for visible lightincluding a wiring or an electrode made of a single-layer conductivefilm, a different example from the Example 4 will be described withreference to FIG. 21. The same reference numerals are used for the sameportions in Example 4.

FIG. 21 shows a photo-sensor for visible light having a structure inwhich the protective electrodes 718, 773, 776, 774 and 775 are notprovided over the wiring 719, the connecting electrode 720, the terminalelectrode 751, the source electrode or drain electrode 771 of the TFT730, and the source electrode or drain electrode 772 of the TFT 731 inFIGS. 13A and 13B, 14A and 14B, 15A to 15C, and 20A to 220D.

In FIG. 21, a wiring 1404, a connecting electrode 1405, a terminalelectrode 1401, a source electrode or drain electrode 1402 of a TFT 731,a source electrode or drain electrode 1403 of a TFT 730 are formed byusing a single-layer conductive film, and as such a conductive film, atitanium film (Ti film) is preferably used. In addition, instead of thetitanium film, single-layer film composed of an element selected fromtungsten (W), tantalum (Ta), molybdenum (Mo), neodymium (Nd), cobalt(Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium(Pd), osmium (Os), iridium (Ir), or platinum (Pt), or an alloy materialor a compound material containing the element as a main component; or asingle-layer film composed of nitride thereof such as titanium nitride,tungsten nitride, tantalum nitride or molybdenum nitride may be used. Byforming the wiring 1404, the connecting electrode 1405, the terminalelectrode 1401, the source electrode or drain electrode 1402 of the TFT731, and the source electrode or drain electrode 1403 of the TFT 730with a single-layer film, the number of deposition can be reduced inmanufacturing steps.

It is to be noted that the present example can be combined with anydescriptions of the Embodiment and the Examples 1 to 5, if necessary.

In accordance with the present invention, a photoelectric conversiondevice in which withstand voltage to electrostatic discharge damage isimproved can be manufactured. Further, by incorporating thephotoelectric conversion device according to the present invention, ahigh reliable electronic device can be obtained.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention hereinafterdescribed, they should be construed as being included therein.

1. A photoelectric conversion device comprising: a photoelectricconversion layer over a substrate, comprising: a first semiconductorlayer having one conductivity type, a second semiconductor layer overthe first semiconductor layer, and a third semiconductor layer having aninverse conductivity type to the one conductivity type, and providedover the second semiconductor layer; a first electrode provided over andin contact with the third semiconductor layer, and in contact with thefirst semiconductor layer through an opening formed in the photoelectricconversion layer; an insulating layer provided over and in contact withthe third semiconductor layer, wherein the insulating layer is spacedfrom the first electrode; and a second electrode provided over theinsulating layer, and in contact with the third semiconductor layerthrough an opening formed in the insulating layer, wherein the thirdsemiconductor layer is selectively provided beneath the first electrodeand the insulating layer.
 2. The photoelectric conversion deviceaccording to claim 1, wherein the substrate is a flexible substrate. 3.The photoelectric conversion device according to claim 2, wherein theflexible substrate comprises a film selected from the group consistingof a polyethylenenaphthalate (PEN) film, a polyethylene terephthalate(PET) film, and a polybutylene naphthalate (PBN) film.
 4. Thephotoelectric conversion device according to claim 1, wherein thesubstrate is a glass substrate.
 5. The photoelectric conversion deviceaccording to claim 1, wherein a conductive film is provided between thesubstrate and the first semiconductor layer.
 6. The photoelectricconversion device according to claim 5, wherein the conductive film is atransparent conductive film.
 7. The photoelectric conversion deviceaccording to claim 1, wherein a color filter is provided between thesubstrate and the first semiconductor layer.
 8. The photoelectricconversion device according to claim 1, wherein the third semiconductorlayer is selectively only provided directly beneath the first electrode,the second electrode, and the insulating layer.
 9. The photoelectricconversion device according to claim 1, wherein the insulating layer isspaced from the first electrode with a gap, and wherein the gap isfilled with a second insulating film.
 10. A semiconductor devicecomprising: a photoelectric conversion element over a substrate; and acircuit for signal processing of an output value of the photoelectricconversion element, wherein the photoelectric conversion elementcomprises: a photoelectric conversion layer comprising: a firstsemiconductor layer having one conductivity type, a second semiconductorlayer provided over the first semiconductor layer, and a thirdsemiconductor layer having an inverse conductivity type to the oneconductivity type of the first semiconductor layer and provided over thesecond semiconductor layer; a first electrode provided over and incontact with the third semiconductor layer, and in contact with thefirst semiconductor layer through an opening formed in the photoelectricconversion layer; an insulating layer provided over and in contact withthe third semiconductor layer, wherein the insulating layer is spacedfrom the first electrode; and a second electrode provided over and incontact with the third semiconductor layer through an opening formed inthe insulating layer, wherein the third semiconductor layer isselectively provided beneath the first electrode and the insulatinglayer; wherein the circuit comprises a plurality of thin filmtransistors; and wherein each of the plurality of thin film transistorscomprises: an island-like semiconductor region comprising a sourceregion, a drain region, and a channel formation region; a gateinsulating film; a gate electrode; a source electrode electricallyconnected to the source region; and a drain electrode electricallyconnected to the drain region.
 11. The semiconductor device according toclaim 10, wherein the circuit is an amplifier circuit to amplify anoutput value of the photoelectric conversion element.
 12. Thesemiconductor device according to claim 10, wherein the substrate is aflexible substrate.
 13. The semiconductor device according to claim 12,wherein the flexible substrate comprises a film selected from the groupconsisting of a polyethylenenaphthalate (PEN) film, a polyethyleneterephthalate (PET) film, and a polybutylene naphthalate (PBN) film. 14.The semiconductor device according to claim 10, wherein the substrate isa glass substrate.
 15. The semiconductor device according to claim 10,wherein a conductive film is provided between the substrate and thefirst semiconductor layer.
 16. The semiconductor device according toclaim 15, wherein the conductive film is a transparent conductive film.17. The semiconductor device according to claim 10, wherein a colorfilter is provided between the substrate and the first semiconductorlayer.
 18. The semiconductor device according to claim 10, wherein eachof the source electrode and the drain electrode is a stacked film. 19.The semiconductor device according to claim 18, wherein the stacked filmis formed by stacking a titanium (Ti) film, an aluminum (Al) filmcontaining a small amount of silicon (Si), and a titanium (Ti) film. 20.The semiconductor device according to claim 10, wherein each of thesource electrode and the drain electrode is a single-layer film.
 21. Thesemiconductor device according to claim 20, wherein the single-layerfilm is a single-layer film composed of an element selected fromtitanium (Ti), tungsten (W), tantalum (Ta), molybdenum (Mo), neodymium(Nd), cobalt (Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium(Rh), palladium (Pd), osmium (Os), iridium (Ir) or platinum (Pt), or analloy material or a compound material containing the element as a maincomponent; or a single-layer film composed of nitride thereof such astitanium nitride, tungsten nitride, tantalum nitride or molybdenumnitride.
 22. The semiconductor device according to claim 10, wherein thethird semiconductor layer is selectively only provided directly beneaththe first electrode, the second electrode, and the insulating layer. 23.The semiconductor device according to claim 10, wherein the insulatinglayer is spaced from the first electrode with a gap, and wherein the gapis filled with a second insulating film.